171228 20260515163946.0 doi 10.1021/acsami.6c04089 sideral 149323 ART-2026-149323 eng Pérez, Estela Macrophage-Mediated In Vivo Intracellular Crystallization of Aluminum Oxyhydroxide Adjuvant in Vaccine-Induced Granulomas 2026 Aluminum (Al) in the form of γ-aluminum oxyhydroxide (γ-AlOOH) nanoparticles has been used as a vaccine adjuvant for nearly a century. At injection sites, animals and humans develop granulomatous inflammation, in which macrophages may contain intracellular crystalline-like structures, so-called crystalloid bodies (CBs), morphologically distinct from the injected adjuvant. This raised the hypothesis that CBs may originate from the in vivo crystallization of γ-AlOOH within macrophages. To test this, six sheep received two subcutaneous doses of a γ-AlOOH-adjuvanted viral vaccine, while six controls received the same antigen without an adjuvant. All injection sites (AlOOH: n = 12; controls: n = 12) were examined by hematoxylin and eosin, modified aluminum hematoxylin, and lumogallion fluorescence. Al and CBs occurred exclusively in AlOOH-vaccinated tissues. The adjuvant stock and vaccine formulations were characterized ex situ using a combination of structural and imaging techniques. Four granulomas containing CBs, collected 133 days postinjection, were further examined using in situ imaging and crystallographic approaches. No crystalline structures resembling CBs were identified in the injected products; only γ-AlOOH nanoparticles were present. In post-mortem granulomas, macrophages contained Al-positive vacuoles filled with nanoparticle aggregates compatible with γ-AlOOH, often adjacent to CBs. Crystallographic analyses demonstrated that CBs were highly ordered γ-Al2O3 microcrystals, and advanced SEM-EDS with elemental mapping similarly distinguished γ-AlOOH nanoparticles and CBs as separate phases. These findings support an in vivo formation of γ-Al2O3 microcrystals from γ-AlOOH nanoparticles within macrophages under physiological conditions. To our knowledge, these findings provide evidence consistent with Al crystallization within mammalian cells and suggest that macrophage phagolysosomal conditions may represent a previously unrecognized biomimetic pathway for γ-Al2O3 formation. This finding may offer a biological model for the development of green and low-energy synthesis strategies for γ-Al2O3, with potential industrial applications as well as relevance to immunotoxicology, pathology, and cell biology in the context of vaccine adjuvants. Access copy available to the general public Unrestricted info:eu-repo/grantAgreement/ES/MCIU/RTI2018-096172-B-C33 info:eu-repo/grantAgreement/ES/MICINN/PID2021-127847OB-I00 info:eu-repo/grantAgreement/ES/MICIU/CEX2023-001286-S info:eu-repo/grantAgreement/ES/MICIU/PID2024–160339OB-I00 info:eu-repo/semantics/openAccess by https://creativecommons.org/licenses/by/4.0/deed.es info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Navarro, Marta Universidad de Zaragoza (orcid)0000-0001-7702-9619 Ibarra, Alfonso Universidad de Zaragoza (orcid)0000-0002-4599-3013 de Blas, Ignacio Universidad de Zaragoza (orcid)0000-0002-1204-4356 Pérez, Marta Universidad de Zaragoza (orcid)0000-0002-8133-2124 Luján, Lluís Universidad de Zaragoza (orcid)0000-0002-2053-9842 Sebastián, Víctor Universidad de Zaragoza (orcid)0000-0002-6873-5244 1009 773 Universidad de Zaragoza Dpto. Patología Animal Área Sanidad Animal 1001 025 Universidad de Zaragoza Dpto. Anatom.,Embri.Genét.Ani. Área Anatom.Anatom.Patológ.Com 5005 555 Universidad de Zaragoza Dpto. Ing.Quím.Tecnol.Med.Amb. Área Ingeniería Química 0 X Universidad de Zaragoza Institutos Univ. de Investig. Área RPT Laboral INMA 18, 18 (2026), 25960-25978 ACS appl. mater. interfaces ACS applied materials & interfaces 1944-8244 5648009 http://zaguan.unizar.es/record/171228/files/texto_completo.pdf Versión publicada 3473746 http://zaguan.unizar.es/record/171228/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:171228 articulos driver 2026-05-15-14:55:30 ARTICLE